Computer system with groups of processor boards

ABSTRACT

A computer system includes a plurality of printed circuit boards, each printed circuit board having one or more processor chips attached to the printed circuit board, wherein the number of printed circuit boards is an even number greater than or equal to 4, wherein the printed circuit boards are arranged in two groups, each group being arranged in a different stacking direction, and wherein the one or more processor chips which are attached to each one of the printed circuit boards of one of the groups are connected for communication to the processor chips of each printed circuit board of the other group.

FOREIGN PRIORITY

This application claims priority to Great Britain Patent Application No.1401654.7, filed Jan. 31, 2014, and all the benefits accruing therefromunder 35 U.S.C. §119, the contents of which in its entirety are hereinincorporated by reference.

BACKGROUND

The present invention relates in general to data processing systems, andin particular, to a computer system with processor boards arranged ingroups with different stacking directions and a method for communicatingacross the processor boards.

In enterprise computer and networking systems, it is often advantageousto utilize high-density computer processing, data storage andtelecommunication hardware components for the processing, storage,switching, routing and transport of high speed data in the form ofdigital signals. It is also advantageous for a plurality of thesevarious components to communicate with each other at very high speedsignaling rates. The use of a component-based system having separationof functions such as processing, storage, switching, and input/outputinterfaces allows individual components to be updated or upgradedindependently from other components as well as allows customization forspecific tasks. Furthermore, the use of components is cost effectivesince developing or purchasing a new component is less expensive thandeveloping or purchasing an entirely new integrated hardware system thatis not based on component design. Some such existing systems arehardwired and use a central switching architecture to allow componentsto communicate with one another.

Furthermore, the modern data center is suffering from the constraints ofcabled, fixed-lane architectures. The concept of interconnecting racksof computing/storage servers through switching equipment with high-speedcables/fibers is taken for granted as the only method for providingconnectivity. The fundamental technique used to provide randomserver-to-server communications is dominated by the Ethernet switch, andin modern data centers the switching architecture is typicallyimplemented through a tiered tree design. A typical equipment rackcontains twenty to forty servers that connect with Ethernet cables tothe top-of-rack (TOR) switch. The TOR switches are then interconnectedto the next tier in the switching system to an end-of-rack (EOR) switch(also known as a cluster switch). The EOR switch is normally a 10gigabit Ethernet (10 GigE) switch with hundreds of ports. TheEOR/cluster switches are then interconnected with 10 GigE (headingtowards 40 GigE in the near future) uplinks to the next tier.

US 2013/0107853 A1 discloses a system and method for wirelesscommunication in a backplane fabric mesh network architecture. Abackplane network comprises a first antenna system located in a firstnetwork device cabinet including at least one first network deviceconfigured to transmit a data message over a high speed backplane. Thefirst antenna system includes a first millimeter wave antenna of thefirst antenna system located external to the first device cabinet andconfigured to communicate with the first network device. The firstmillimeter wave antenna is configured to wirelessly transmit the datamessage from the first network device over the high speed backplaneusing emitted millimeter wave electromagnetic radiation. The networkincludes a second antenna system located in a second network devicecabinet including at least one second network device, wherein the firstand second device cabinets are positioned spatially apart from oneanother. The second antenna system includes a second millimeter waveantenna of the antenna system coupled to the second antenna system andlocated external to the second device cabinet. The second millimeterwave antenna is configured to wirelessly receive the data message overthe high speed backplane using millimeter wave electromagnetic radiationemitted from the second millimeter wave antenna, wherein the receiveddata message is handled by the second network device, the entirecommunication being handled without a central switch.

SUMMARY

In one embodiment, a computer system includes a plurality of printedcircuit boards, each printed circuit board having one or more processorchips attached to the printed circuit board; wherein the number ofprinted circuit boards is an even number greater than or equal to 4, theprinted circuit boards are arranged in two groups, each group beingarranged in a different stacking direction, and wherein the one or moreprocessor chips which are attached to each one of the printed circuitboards of one of the groups are connected for communication to theprocessor chips of each printed circuit board of the other group.

In another embodiment, a method is disclosed for connecting andcommunicating across a plurality of printed circuit boards of a computersystem, each printed circuit board comprising one or more processorchips attached to the printed circuit board, wherein the number ofprinted circuit boards is an even number greater than or equal to 4. Themethod includes arranging the printed circuit boards in two groups, eachgroup being arranged in a different stacking direction; and connectingthe one or more processor chips, which are attached to each one of theprinted circuit boards of one of the groups, for communication to theprocessor chips of each printed circuit board of the other group.

In another embodiment, a computer readable storage medium havingcomputer readable instructions stored thereon that, when executed by acomputer, implement a method for connecting and communicating across aplurality of printed circuit boards of a computer system, each printedcircuit board comprising one or more processor chips attached to theprinted circuit board, wherein the number of printed circuit boards isan even number greater than or equal to 4. The method includes arrangingthe printed circuit boards in two groups, each group being arranged in adifferent stacking direction; and connecting the one or more processorchips, which are attached to each one of the printed circuit boards ofone of the groups, for communication to the processor chips of eachprinted circuit board of the other group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a computer system according to an embodiment of the invention,comprising 16 processor chips on two groups of 8 printed circuit boardseach;

FIG. 2 is a computer system according to an embodiment of the invention,comprising 32 processor chips on two groups of 8 printed circuit boardseach;

FIG. 3 is a printed circuit board with 2 processor chips according tothe embodiment of the invention described in FIG. 2;

FIG. 4 is a printed circuit board with 4 processor chips according toanother embodiment of the invention;

FIG. 5 is a printed circuit board with 3 processor chips according toanother embodiment of the invention;

FIG. 6 is a computer system according to a further embodiment of theinvention, comprising 8 processor chips on two groups of 4 printedcircuit boards each;

FIG. 7 is a printed circuit board with one processor chip according toan embodiment of the invention, exhibiting coherent shared memoryaccess;

FIG. 8 is a printed circuit board with one processor chip according to afurther embodiment of the invention, exhibiting non-coherent sharedmemory access;

FIG. 9 is a printed circuit board with one processor chip according toanother embodiment of the invention, exhibiting a PCI-connection for anexpansion card;

FIG. 10 is a printed circuit board with one processor chip according toa further embodiment of the invention, exhibiting message passing usinga network protocol for communication;

FIG. 11 is a printed circuit board with two processor chips according toa further embodiment of the invention, where each processor chip isconnected to only a subset of the connectors of the printed circuitboard;

FIG. 12 is a printed circuit board with four processor chips accordingto a further embodiment of the invention, where two processor chips areconnected to only two other processor chips of the same printed circuitboard;

FIG. 13 is a printed circuit board with a network router and networkinterface controllers connected to processor chips according to afurther embodiment of the invention; and

FIG. 14 is an example embodiment of a data processing system forcarrying out a method according to the invention.

DETAILED DESCRIPTION

Aspects of the invention provide a computer system with multipleprocessor boards being interconnected in a space and cost saving manner,as well as to provide a method for connecting and communicating acrossmultiple processor boards of a computer system being interconnected in aspace and cost saving manner. These aspects are achieved by the featuresof the independent claims. The other claims, the drawings and thespecification disclose advantageous embodiments of the invention.

According to a first aspect of the invention a computer system isproposed, comprising a plurality of printed circuit boards, each printedcircuit board comprising one or more processor chips attached to theprinted circuit board, wherein the number of printed circuit boards isan even number greater than or equal to 4, wherein the printed circuitboards are arranged in two groups each group being arranged in adifferent stacking direction and wherein the one or more processor chipswhich are attached to each one of the printed circuit boards of one ofthe groups are connected for communication to the processor chips ofeach printed circuit board of the other group.

A processor board may thus be implemented as a printed circuit boardwith one or more processor chips attached to it. The processor chips maybe connected for communication via electrical and/or optical connectionto the connectors of a printed circuit board and/or other processorchips on the same printed circuit board. The connections from theconnectors of a printed circuit board to at least one processor chip ofthe printed circuit board may comprise power connections andcommunication connections as well.

The processor chips may be directly connected to the processor chips ofother printed circuit boards or alternatively routed via other processorchips on the same printed circuit board thus communicating via processorchips on the same printed circuit board to other processor chips. Thesame applies to the processor chip to be communicated to, which too doesnot need to be connected directly but may also be routed through otherprocessor chips on its printed circuit board.

Thus several embodiments for connection of processor chips attached toprinted circuit boards according to the invention may exist:

Each processor chip connects to each processor chip on each printedcircuit board of the other group of printed circuit boards.

Each processor chip connects to its peer processor chip on each otherprinted circuit board of the other group of printed circuit boards.

An individual processor chip only connects to some other printed circuitboards in the other group.

An individual processor chip may not be directly connected to processorchips on other printed circuit boards. Such a processor chip onlyconnects to processor chips on the same printed circuit board.

Embodiments of the invention relate to a computer system implemented asa cost-efficient, high-performance large multiprocessor system with, forexample, 16, 32 or 64 processor chips. Due to limitations of knownsolutions, applications requiring many processor chips typically use acluster of small multiprocessor systems, where each multiprocessorsystem has 2 or 4 processor chips. The invention allows an applicationto use a single large multiprocessor system with, e.g., 64 processorchips, or a cluster of large multiprocessor systems, thus reducing costsor increasing performance. The printed circuit boards may exhibitdifferent numbers of processor chips, e.g., printed circuit boards with4 processor chips may be mixed with printed circuit boards with 2processor chips. Thus it is possible to conceptually extend amultiprocessor system for higher number of processor chips, e.g., from32 processor chips to 64 processor chips, without increasing thebandwidth of communication across the printed circuit boards, butinstead increasing the number of hops for the communication from aspecific processor chip on one printed circuit board to the processorchip on another printed circuit board of the same or another group ofprinted circuit boards. Also tailored systems may be implemented with adedicated number of processor chips according to a specific application.

Embodiments of the invention describe a computer system, favorably of ashared memory type, comprising a group of printed circuit boards stackedin one direction connected for communication to a group of printedcircuit boards stacked in another direction. The first group of printedcircuit boards may be stacked, e.g., horizontally whereas the secondgroup may be stacked vertically. Thus a multiprocessor system with 16processor chips, e.g., may comprise a chassis with 8 vertical printedcircuit boards (often called as blades) and 8 horizontal printed circuitboards, whereas a vertical printed circuit board shows the sameconfiguration than the horizontal printed circuit board except for theorientation of the connectors. Each printed circuit board may comprise aprocessor chip which exhibits 8 connections, each to a board to boardconnector connected to the processor chip of each of the printed circuitboards of the other group.

Thus, embodiments of the invention describe a way to implement acomputer system with a large number of processor chips interacting,avoiding the costly typical backplane or midplane in a chassis housing alarge number of printed circuit boards. The inventive solution alsoserves for space saving in designing chassis for multiprocessor systemsas it exhibits a very compact manner of interconnecting printed circuitboards with processor chips in direct connections from each one printedcircuit board of one group to each printed circuit board of the othergroup. Thus it may be very convenient to change or remove an individualprinted circuit board by simply unplugging it from the printed circuitboards of the other group without further disassembly of the computersystem. A further advantage of the inventive solution is that allprinted circuit boards may be identical thus realizing a verycost-efficient way of implementing a multiprocessor computer system.

Favorably, the stacking directions of the two groups of printed circuitboards may be arranged orthogonally. Stacking the printed circuit boardsvertically in one group whereas stacking the printed circuit boardshorizontally in another group of printed circuit boards is a veryconvenient and efficient way of arranging the printed circuit boards.Also it is very convenient for arranging the connectors for connectingthe printed circuit boards of one group to the other group.Manufacturing of such a chassis for a multiprocessor system may also bevery favorable.

Due to an advantageous embodiment, a processor chip may be connected toa memory device. Thus a printed circuit board is a common processorplatform with a corresponding memory device for running the processorchip on its own and also enabling a shared memory access to all otherprocessor chips connected to through the processor chip of a printedcircuit board.

Favorably, the connection of the processor chip to a correspondingmemory device may be performed using a memory subsystem. This memorysubsystem may serve as an interface between the processor chip and astandard memory device like a DRAM (dynamic random access memory) memorychip, such as a DIMM (dual inline memory module) chip, which is afrequently used memory type in multiprocessor systems.

In an advantageous embodiment, the printed circuit board of one of thegroups may be connected to each of the printed circuit boards of theother group via at least one connector of a plug type or a socket typeor a combined plug and socket type. The printed circuit boards thus mayexhibit the same layout except that the printed circuit boards of onegroup of printed circuit boards may exhibit plug type connectors and theprinted circuit boards of the other group may exhibit socket typeconnectors. Alternatively it is thinkable that there may exist a mixedtype connector which is a combined plug and socket type connector andwhich enables to use only one type of connector. Thus the printedcircuit boards could exhibit the same layout each in either group ofprinted circuit boards.

Advantageously, the one or more processor chips on at least one of theprinted circuit boards may be directly connected to the at least oneconnector on the same printed circuit board and, if more than oneprocessor chip is on the printed circuit board, to all other processorchips on the same printed circuit board. By this way the processor chipmay be connected and communicating to the processor chips on all theprinted circuit boards of the other group of printed circuit boards ofthe computer system. A processor chip in one group may routecommunication across two processor chips in different boards in theother group. By this way the processor chip may be communicating to theprocessor chips on all the printed circuit boards of the same group ofprinted circuit boards of the computer system. Additionally theprocessor chip may be connected to all other processor chips on the sameprinted circuit board. A processor chip thus can communicate andexchange information as well as perform a shared memory access acrossall processor chips of the computer system.

In a favorable embodiment, at least one processor chip on at least oneof the printed circuit boards of one of the groups may comprise anetwork interface. Software on the processor core of the processor chipmay configure the local network interface to exchange one or moremessages with the network interfaces on the other printed circuitboards. Thus a processor core may communicate via message passing acrossthe various printed circuit boards.

Advantageously, the one or more processor chips which are attached toeach one of the printed circuit boards of one of the groups may beconnected to each of the processor chips of all printed circuit boardsof the other group via at least one network router and a networkinterface controller. In such an arrangement a cluster of processorchips may be configured on the printed circuit board wherein one or moreprocessor chips are connected to the at least one network router via anetwork interface controller. Such a configuration may be used on eachof the printed circuit boards of a multiprocessor system. Thus ascalable network may be customized in the inventive multiprocessorsystem with, e.g., 2 network interface controllers arranged on a printedcircuit board for a 32 processor system and with 4 network interfacecontrollers arranged on a printed circuit board for a 64 processorsystem. Such a configuration is very flexible to be scaled even on largemultiprocessor systems as well as may be distributed over a largemultiprocessor system if needed for speed of access and reliability.

In a favorable embodiment, at least one processor chip on a printedcircuit board of one of the groups may be connected to a PCI Expresscard providing access to the PCI Express card for at least one processorchip on another printed circuit board of the same or another group.Thus, a very efficient use of resources in a multiprocessor system canbe implemented.

According to a further advantageous aspect of the invention, a methodfor connecting and communicating across a plurality of printed circuitboards of a computer system is proposed, each printed circuit boardcomprising one or more processor chips attached to the printed circuitboard, wherein the number of printed circuit boards is an even numbergreater than or equal to 4, wherein the printed circuit boards arearranged in two groups each group being arranged in a different stackingdirection, and wherein the one or more processor chips which areattached to each one of the printed circuit boards of one of the groupsare connected for communication to the processor chips of each printedcircuit board of the other group.

The invention relates to communication within a cost-efficient,high-performance large multiprocessor system with, for example, 16, 32or 64 processor chips. Applications requiring many processors typicallyuse a cluster of small multiprocessor systems, where each multiprocessorsystem has 2 or 4 processor chips. The invention allows an applicationto use a single large multiprocessor system with, e.g., 64 processorchips, or a cluster of large multiprocessor systems, thus reducing costsor increasing performance.

Thus, embodiments of the invention describe a way to implement amultiprocessor system with a large number of processors interacting andavoiding the costly typical backplane or midplane in a chassis housing alarge number of printed circuit boards.

The inventive solution also serves for space saving in designing chassisfor multiprocessor systems.

Advantageously, the communication across the processor chips may beperformed via a coherent shared memory access, which means that eachprocessor chip has a coherent cached access to the memory of anotherprocessor chip, e.g., a DRAM memory device, such as a DIMM chip. Thismay serve for implementing scalable memory solutions for applications ofa multiprocessor system in a very convenient and cost saving way. Thusmemory and network traffic may be reduced especially in largemultiprocessor systems.

Alternatively, the communication across the processor chips may beperformed via a non-coherent shared memory access, meaning that eachprocessor chip has load/store access to the memory of another processorchip, e.g., a DRAM memory device, such as a DIMM chip. For certainapplications this may be a favorable way of accessing memory resources.

In another embodiment, the communication across the processor chips mayprovide a processor chip usage access to a graphics, storage,communication or other adapter card attached via the PCI (peripheralcomponent interconnect)—interface to another processor chips. PCI is acommonly used standard interface description for connecting peripheraldevices.

Due to an alternative embodiment, the communication across the processorchips may also be performed via message passing using a networkprotocol, like Ethernet, Infiniband or a proprietary protocol. Messagepassing is also a frequently used standard for the exchange ofinformation in distributed computer systems. Message passing is based ona plurality of processes communicating to each other via messages whichare sent from one process to another designated process, using a highspeed network for exchange. One of the advantages is that communicationalso functions across the borders of different computer systems.

Favorably, the communication across the processor chips may be performedusing communication between two or more processor chips on the sameprinted circuit board. In this embodiment each of the processor chipsmay not be directly connected to the connector of the printed circuitboard. Therefore communication from one processor chip of anotherprinted circuit board may be routed through a second processor chip onthe same printed circuit board which is directly connected to theconnector of the printed circuit board. Even a processor chip may not beconnected to the connector but only to other processor chips on the sameprinted circuit board.

Advantageously, the communication across the processor chips may beperformed via at least one network router and a network interfacecontroller connected to at least one processor chip on at least oneprinted circuit board. In such an arrangement, a cluster of processorchips may be configured on the printed circuit board wherein one or moreprocessor chips are connected to the at least one network router via anetwork interface controller. Such a configuration may be used on eachof the printed circuit boards of a multiprocessor system.

Due to the inventive solution a printed circuit board may be unconnectedby previously idling its one or more processor chip via a hypervisorrunning on the computer system. A printed circuit board may be needed tobe removed from the multiprocessor system for service and thereforeshall be unlogged from the operating system. This may be performed by ahypervisor of typical operating systems as used in multiprocessorsystems, such as Linux or AIX. The remaining printed circuit boards thusrepresent the multiprocessor system with a reduced number of processorscommunicating with a reduced aggregate bandwidth due to the removedprinted circuit board comprising one or more processor chips, whereasthe computer system remains still functioning.

Advantageously, the communication may be tracked by a precise directory,thus exhibiting a directory based cache coherence for shared memoryaccess across the plurality of processor chips of the computer system.The precise directory thus tracks all the processor chips in thecomputer system and controls the communication across the processorchips.

According to a further advantageous aspect of the invention, a dataprocessing program for execution in a data processing system is proposedcomprising an implementation of an instruction set for performing amethod as described above when the data processing program is run on acomputer.

Further a favorable computer program product is proposed comprising acomputer usable medium including a computer readable program, whereinthe computer readable program when executed on a computer causes thecomputer to perform a method for connecting and communicating across aplurality of printed circuit boards of a computer system, each printedcircuit board comprising one or more processor chips attached to theprinted circuit board, wherein the number of printed circuit boards isan even number greater than or equal to 4, wherein the printed circuitboards are arranged in two groups each group being arranged in adifferent stacking direction, and wherein the one or more processorchips which are attached to each one of the printed circuit boards ofone of the groups are connected for communication to each of theprocessor chips of all printed circuit boards of the other group.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”

Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device. A computer readable signal medium may include apropagated data signal with computer readable program code embodiedtherein, for example, in baseband or as part of a carrier wave. Such apropagated signal may take any of a variety of forms, including, but notlimited to, electro-magnetic, optical, or any suitable combinationthereof. A computer readable signal medium may be any computer readablemedium that is not a computer readable storage medium and that cancommunicate, propagate, or transport a program for use by or inconnection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wire connection, optical fiber cable, RF, etc., or any suitablecombination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toblock diagrams of methods, apparatus (systems) and computer programproducts according to embodiments of the invention. It will beunderstood that each block of the flowchart illustrations and/or blockdiagrams, and combinations of blocks in the block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the block diagram block orblocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the block diagram block orblocks.

Due to a further aspect of the invention, a data processing system forexecution of a data processing program is proposed, comprising softwarecode portions for performing a method described above.

In the drawings, like elements are referred to with equal referencenumerals. The drawings are merely schematic representations, notintended to portray specific parameters of the invention. Moreover, thedrawings are intended to depict only typical embodiments of theinvention and therefore should not be considered as limiting the scopeof the invention.

Referring now to FIG. 1, a computer system 212 according to anembodiment of the invention is shown, comprising 16 processor chips 12,30 on two groups 14, 16 of 8 printed circuit boards 10 each. Thecomputer system 212 is comprising a plurality of 16 printed circuitboards 10, each printed circuit board 10 comprising one or moreprocessor chips 12, 30 attached to the printed circuit board 10, whereinthe number of printed circuit boards 10 is an even number greater thanor equal to 4, namely 16 in the embodiment shown, wherein the printedcircuit boards 10 are arranged in two groups 14, 16, each group 14, 16being arranged in a different stacking direction 50, 52, and wherein theone or more processor chips 12, 30 which are attached to each one of theprinted circuit boards 10 of one of the groups 14 are directly connectedfor communication to a processor chip 30, 12 of each printed circuitboard 10 of the other group 16. The stacking directions 50, 52 of thetwo groups 14, 16 are arranged orthogonally in the embodiment shown.Each processor chip 12, 30 is connected 46 to a memory device 18. Eachprinted circuit board 10 of one of the groups 14, 16 is connected toeach printed circuit board 10 of the other group 16, 14 via at least oneconnector 22 of a plug type or a socket type or a combined plug andsocket type. There may be one single connector type on a printed circuitboard 10. Alternatively the connections may also be arranged in morethan one connector type on a single printed circuit board 10. The oneprocessor chip 12, 30 on at least one of the printed circuit boards 10is directly connected to the at least one connector 22 on the sameprinted circuit board 10 via connections 36, 42.

At least one processor chip 12 on at least one of the printed circuitboards 10 of one of the groups 14, 16 may comprise a network interface68 (see FIG. 10). Software on the processor chip 12 may configure thelocal network interface 68 to exchange one or more messages with thenetwork interfaces 68 on the other printed circuit boards. Thus theprocessor chip 12 may communicate via message passing across the variousprinted circuit boards 10.

The computer system 212 shown in FIG. 1 may implement a method forconnecting and communicating across the plurality of printed circuitboards 10 of the computer system 212, wherein the one or more processorchips 12, 30 which are attached to each one of the printed circuitboards 10 of one of the groups 14, 16 are directly connected forcommunication to the processor chips 30, 12 of each printed circuitboard 10 of the other group 16, 14. A direction connection is processor30 over connection 42 to connector 22 over connection 36 to processor 12of the other group 14. In other words a processor chip 30 has a one hopcommunication with a processor 12 in the other group 14. A processorchip 30 in one group 16 may route communication across two processorchips 12 in different boards 10 in the other group 14. By this way theprocessor chip 30 may be communicating to the processor chips 30 on allthe printed circuit boards 10 of the same group 16 of printed circuitboards 10 of the computer system 212. In other words, a processor chip30 has a two hop communication with a processor chip 30 in the samegroup 16. The communication across the processor chips 12, 30 may beperformed e.g., via a non-coherent or coherent shared memory access. Thecommunication may be tracked by a precise directory.

If a printed circuit board 10 shall be removed from the computer system212, e.g., for service, the printed circuit board 10 may be unconnectedby previously idling the processor chip 12 via a hypervisor running onthe computer system 212. The computer system 212 may run with adifferent number of printed circuit boards 10 in each group 14, 16.

In FIG. 2, a computer system 212 according to an embodiment of theinvention is shown, comprising 32 processor chips 12, 28, 30, 32 on twogroups 14, 16 of 8 printed circuit boards 10 each. The processor chips12, 28, 30, 32 are connected via connections 46 to their correspondingmemory devices 18. Processor chip 12 is further connected to theconnectors 22 via connections 36, processor chip 28 via connections 40,processor chip 30 via connections 42, and processor chip 32 viaconnections 44. The interconnection between processor chips 12 and 28,as well as between processor chips 30 and 32 is performed usingconnections 38. In a first alternative without the dashed connections 42and 40, processor chip 32 on each card in its group is directlyconnected to its so-called peer processor chip 12 on each card in theother group. Processor chip 32 thus has two hops to its non-peerprocessor chip 28 via processor chip 12 on each card in the other group.Processor chip 32 thus has three hops to its non-peer processor chip 30on each other card in its own group. In a second alternative with thedashed connections 42 and 40, processor chip 32 on each card in itsgroup is directly connected to both processor chip 12 and to processorchip 28 on each card in the other group. Processor chip 32 thus has onehop to either processor chip 12 or 28 on each card in the other group.Processor chip 32 thus has two hops to either processor chip 30 or 32 oneach other card in its own group.

FIG. 3 depicts a printed circuit board 10 with 2 processor chips 30, 32according to the embodiment of the invention described in FIG. 2. Theprocessor chips 30, 32 are connected via connections 46 to theircorresponding memory devices 18. Processor chip 30 is further connectedto the connectors 22 via connections 42, processor chip 32 viaconnections 44. The interconnection between processor chips 30 and 32 isperformed using connection 38. At connector 22, connection 42 does nottypically connect nor partially connect to connection 44. Thus thedashed connection 42 is only an alternative embodiment for theconnection of a processor chip 30 to the connectors 22 instead ofprocessor chip 32.

In FIG. 4, a printed circuit board 10 is shown with 4 processor chips12, 28, 30, 32 according to another embodiment of the invention. Theprocessor chips 12, 28, 30, 32 are connected via connections 46 to theircorresponding memory devices 18. Processor chip 12 is further connectedto the connectors 22 via connections 36, processor chip 28 viaconnections 40, processor chip 30 via connections 42, and processor chip32 via connections 44. The connections 36 and 44 are depicted as asingle connection each for simplification of the Figure. The connections36, 40, 42 and 44 are to be understood as alternative connections whichmay only partially be implemented. Only one of them is necessary for thefunctioning of the printed circuit board 10. The interconnection betweenthe processor chips 12, 28, 30 and 32 to each other is performed usingconnections 38.

FIG. 5 depicts a printed circuit board 10 with 3 processor chips 12, 28,30 according to another embodiment of the invention. The processor chips12, 28, 30 are connected via connections 46 to their correspondingmemory devices 18. Processor chip 12 is further connected to theconnectors 22 via connections 36, processor chip 28 via connections 40,and processor chip 30 via connections 42. The connections 42 aredepicted as a single connection for simplification of the Figure. Again,the connections 36, 40 and 42 are to be understood as alternativeconnections which may only partially be implemented. Only one of them isnecessary for the functioning of the printed circuit board 10. Theinterconnection between the processor chips 12, 28, and 30 to each otheris performed using connections 38.

FIG. 6 shows a computer system 212 according to a further embodiment ofthe invention, comprising 8 processor chips 12, 30 on two groups 14, 16of 4 printed circuit boards 10 each. In this embodiment the connectionof the processor chip 12 to a corresponding memory device 18 isperformed using connection 46. The processor chip 12 is connected viaconnections 36 to the connectors 22 of the printed circuit board 10. Ingroup 16 connection of the processor chip 30 to a corresponding memorydevice 18 is also performed via connection 46. The processor chip 30 isconnected via connections 42 to the connectors 22 of the printed circuitboard 10. It should be emphasized that 4+4 printed circuit boards, orother number N+N printed circuit boards are possible, instead of 8+8printed circuit boards shown in other Figures.

In FIG. 7, a printed circuit board 10 with one processor chip 12according to an embodiment of the invention is shown, exhibitingcoherent shared memory access. The processor chip 12 comprises a router60 which is connected to the connectors 22 of the printed circuit board10 via connections 36 thus directly connected to the routers 60 of eachprinted circuit board 10 of the other group 16 of the computer system212. Further, the router 60 is connected to a memory subsystem 20 viaconnection 74. The memory subsystem 20 is connected to a processor core62 via connection 75 and to a memory device 18, e.g., a DRAM memorydevice like a DIMM chip, via connection 76. The local memory subsystem20 may cache a copy of some memory contents from another processor chip28 in the computer system 212. A direction connection is processor 12via router 60 over connection 36 to connector 22 to the router 60 of aprocessor 30 of the other group 16. In other words a processor chip 12has a one hop communication with a processor 12 in the other group 14.The router 60 of a processor chip 30 in one group 16 may routecommunication across the routers 60 of two processor chips 30 indifferent boards 10 in the other group 16. By this way the processorchip 12 may be communicating to the processor chips 12 on all theprinted circuit boards 10 of the same group 14 of printed circuit boards10 of the computer system 212. In other words, a processor chip 12 has atwo hop communication with a processor chip 12 in the same group 14.

FIG. 8 shows a printed circuit board 10 with one processor chip 12according to a further embodiment of the invention, exhibitingnon-coherent shared memory access. The processor chip 12 comprises arouter 60 which is connected to the connectors 22 of the printed circuitboard 10 via connections 36 thus communicating to the routers 60 of allother printed circuit boards 10 of the computer system 212. Further therouter 60 is connected to a processor core 62 via connection 78, whereasthe processor core 62 itself is connected to a memory device 18, e.g., aDRAM memory device like a DIMM chip, via connection 77. As the processorchip 12 has direct load/store access to the memory device 18 of anyother processor chip 28, via its own router 60 and that of the otherprocessor chip 30, there is no need for a local cache copy. A directionconnection is processor 12 via router 60 over connection 36 to connector22 to the router 60 of a processor 30 of the other group 16. In otherwords a processor chip 12 has a one hop communication with a processor12 in the other group 14. The router 60 of a processor chip 30 in onegroup 16 may route communication across the routers 60 of two processorchips 30 in different boards 10 in the other group 16. By this way theprocessor chip 12 may be communicating to the processor chips 12 on allthe printed circuit boards 10 of the same group 14 of printed circuitboards 10 of the computer system 212. In other words, a processor chip12 has a two hop communication with a processor chip 12 in the samegroup 14.

In FIG. 9, a printed circuit board 10 with one processor chip 12according to another embodiment of the invention is shown, exhibitingPCI-connection 82 for an expansion card 66. The processor chip 12comprises a router 60 which is connected to the connectors 22 of theprinted circuit board 10 via connections 36 thus communicating to therouters 60 of the processor chips all other printed circuit boards 10 ofthe computer system 212. Further the router 60 is connected to a memorysubsystem 20, via connection 74. The memory subsystem 20 is connected toa processor core 62 via connection 75 and to a memory device 18, e.g., aDRAM memory device like a DIMM chip, via connection 76. The local memorysubsystem 20 may cache a copy of the memory device 18 of any otherprocessor chip 28. The memory subsystem 20 is connected to a PCI Expresshost 64 on the processor chip 12 via connection 80, which provides aPCI-connection 82 for a PCI Express card 66. Access to the PCI Expresscard 66 for other processor chips 28 on other printed circuit boards 10of the same group 14 or another group 16 is provided via the router 60of the processor chips 12.

For example, the PCI Express card 66 may be a network card for externalcommunication of the computer system 212 via Ethernet or the like.

FIG. 10 shows a printed circuit board 10 with one processor chip 12according to a further embodiment of the invention, exhibiting messagepassing using a network protocol for communication. In this embodimentthe router 60 is connected to a network interface 68 which is connectedvia connection 86 to a memory subsystem 20, wherein the memory subsystem20 is connected to a processor core 62 and a memory device 18 as inother embodiments with coherent shared memory access. Software on theprocessor core 62 configures the local network interface 68 to exchangeone or more messages with the network interfaces 68 on the other printedcircuit boards 10. Thus the computer system 212 may refer to themultiple printed circuit boards 10 as a computer cluster. In variousscenarios, message passing may provide features or performance betterthan shared memory access. Various systems may support both messagepassing and shared memory across processor cores 62.

In FIG. 11, a printed circuit board 10 with two processor chips 30, 32according to a further embodiment of the invention is shown, where eachprocessor chip 30, 32 is connected to only a subset of the connectors 22of the printed circuit board 10. With two or more processor chips 30, 32on a printed circuit board 10, each processor chip 30, 32 might not bedirectly connected to all the connectors 22 on the printed circuit board10. Thus, a communication packet destined for this printed circuit board10 might arrive on a link of the destination processor chip 30.Otherwise, the communication packet might hop through another processorchip 32. Similarly for a communication packet hopping through thisprinted circuit board 10. If incoming and outgoing connectors 22 areattached to the same processor chip 30, then the packet might hop justthrough that processor chip 30. Otherwise, it might hop through bothprocessor chips 30, 32. Also, it should be mentioned that on a printedcircuit board 10, a processor chip 30 may be connected to any otherprocessor chip 32 on the same printed circuit board 10, but not beconnected to the connectors 22 of the printed circuit board 10 indicatedby the dashed connection 42 to the connectors 22. Therefore, ifprocessor chip 30 is communicating to processor chips 12, 28 of printedcircuit boards 10 of another group 14 then communication is running overprocessor chip 32 then to the processor chips 12, 18 on other printedcircuit boards 10 of the other group 14 or to processor chips 30, 32 ofthe same group 16 involving additional hopping of communication acrossprocessor chips 32, 12, 28.

FIG. 12 shows a printed circuit board 10 with four processor chips 12,28, 30, 32 according to a further embodiment of the invention. The twoprocessor chips 12, 28 in this case are connected to only two otherprocessor chips 30, 32 of the same printed circuit board 10, but notdirectly to the connectors 22 of the printed circuit board 10. Thus,communicating to processor chips 12 of other printed circuit boards 10of the same group 14 or another group 16 of printed circuit boards 10communication may hop over the processor chip 30 or the processor chip32 via connections 38 to reach processor chips 12 on other printedcircuit boards 10. Even only one processor chip 32 may be connected tothe connectors 22 and thus to other printed circuit boards 10 as isindicated by the dashed connections 42. In this case also communicationfrom processor chip 30 hops via processor chip 32 to reach otherprocessor chips 12 on other printed circuit boards 10.

FIG. 13 shows a printed circuit board 10 with a network router 70 andnetwork interface controllers 72 connected to processor chips 12, 28according to a further embodiment of the invention. The network router70 is connected to the connectors 22 via connections 88 and to thenetwork interface controllers 72 via connections 90. The processor chips12, 28 are connected via connections 92 to the network interfacecontrollers 72. In such an arrangement a cluster of processor chips 12,28 may be configured on the same printed circuit board 10 wherein one ormore processor chips 12, 28 are connected to the at least one networkrouter 70 via a network interface controller 72. Such a configurationmay be used on each of the printed circuit boards 10 of a multiprocessorsystem.

Referring now to FIG. 14, a schematic of an example of a data processingsystem 210 is shown. Data processing system 210 is only one example of asuitable data processing system and is not intended to suggest anylimitation as to the scope of use or functionality of embodiments of theinvention described herein. Regardless, data processing system 210 iscapable of being implemented and/or performing any of the functionalityset forth herein above.

The data processing system 210 is capable of running a computer programproduct comprising a computer usable medium including a computerreadable program, wherein the computer readable program when executed ona computer system 212 causes the computer system 212 to perform a methodfor connecting and communicating across a plurality of printed circuitboards 10 of a computer system 212, each printed circuit board 10comprising one or more processor chips 12, 28, 30, 32 attached to theprinted circuit board 10, wherein the number of printed circuit boards10 is an even number greater than or equal to 4, wherein the printedcircuit boards 10 are arranged in two groups 14, 16, each group 14, 16being arranged in a different stacking direction 50, 52, and wherein theone or more processor chips 12, 32 which are attached to each one of theprinted circuit boards 10 of one of the groups 14, 16 are connected forcommunication to the processor chips 28, 30 of each printed circuitboard 10 of the other group 16, 14.

In data processing system 210 there is a computer system/server 212,which is operational with numerous other general purpose or specialpurpose computing system environments or configurations. Examples ofwell-known computing systems, environments, and/or configurations thatmay be suitable for use with computer system/server 212 include, but arenot limited to, micro-controllers, personal computer systems, servercomputer systems, thin clients, thick clients, handheld or laptopdevices, multiprocessor systems, microprocessor-based systems, set topboxes, programmable consumer electronics, network PCs, minicomputersystems, mainframe computer systems, and distributed cloud computingenvironments that include any of the above systems or devices, and thelike.

Computer system/server 212 may be described in the general context ofcomputer system executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 212 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 14, computer system/server 212 in data processingsystem 210 is shown in the form of a general-purpose computing device.The components of computer system/server 212 may include, but are notlimited to, one or more processors or processing units 216, a systemmemory 228, and a bus 218 that couples various system componentsincluding system memory 228 to processor 216. Bus 218 represents one ormore of any of several types of bus structures, including a memory busor memory controller, a peripheral bus, an accelerated graphics port,and a processor or local bus using any of a variety of busarchitectures. By way of example, and not limitation, such architecturesinclude Industry Standard Architecture (ISA) bus, Micro ChannelArchitecture (MCA) bus, Enhanced ISA (EISA) bus, Video ElectronicsStandards Association (VESA) local bus, and Peripheral ComponentInterconnect (PCI) bus.

Computer system/server 212 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 212, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 228 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 230 and/or cachememory 232. Computer system/server 212 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 234 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 218 by one or more datamedia interfaces. As will be further depicted and described below,memory 228 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 240, having a set (at least one) of program modules 242,may be stored in memory 228 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data.

Each of the operating system, one or more application programs, otherprogram modules, and program data or some combination thereof, mayinclude an implementation of a networking environment. Program modules242 generally carry out the functions and/or methodologies ofembodiments of the invention as described herein.

Computer system/server 212 may also communicate with one or moreexternal devices 214 such as a keyboard, a pointing device, a display224, etc.; one or more devices that enable a user to interact withcomputer system/server 212; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 212 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 222. Still yet, computer system/server 212can communicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 220. As depicted, network adapter 220communicates with the other components of computer system/server 212 viabus 218. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 212. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

The block diagrams in the figures illustrate the architecture,functionality, and operation of possible implementations of systems,methods and computer program products according to various embodimentsof the present invention. In this regard, each block in the blockdiagrams may represent a module, segment, or portion of code, whichcomprises one or more executable instructions for implementing thespecified logical functions. It should also be noted that, in somealternative implementations, the functions noted in the block may occurout of the order noted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams, and combinations of blocks in the block diagrams, can beimplemented by special purpose hardware-based systems that perform thespecified functions or acts, or combinations of special purpose hardwareand computer instructions.

The invention claimed is:
 1. A computer system, comprising: a pluralityof printed circuit boards, each printed circuit board comprising two ormore processor chips attached to the printed circuit board and aplurality of connectors, wherein a first subset of the two or moreprocessor chips are connected to a first subset of the plurality ofconnectors and wherein a second subset of the two or more processorchips are connected to a second subset of the plurality of connectors;wherein the number of printed circuit boards is an even number greaterthan or equal to 4, the printed circuit boards are arranged in twogroups, each group being arranged in a different stacking direction, andwherein the two or more processor chips which are attached to each oneof the printed circuit boards of one of the groups are connected forcommunication to the processor chips of at least one printed circuitboard of the other group.
 2. The computer system according to claim 1,wherein the stacking directions of the two groups are arrangedorthogonally.
 3. The computer system according to claim 1, wherein aprocessor chip is connected to a memory device.
 4. The computer systemaccording to claim 1, wherein the connection of the processor chip to acorresponding memory device is performed using a memory subsystem. 5.The computer system according to claim 1, wherein the printed circuitboard of one of the groups is connected to each of the printed circuitboards of the other group via at least one connector of a plug type or asocket type or a one combined plug and socket type.
 6. The computersystem according to claim 1, wherein the one or more processor chips onat least one of the printed circuit boards is connected to the at leastone connector on the same printed circuit board and, if more than oneprocessor chip is on the printed circuit board, to all other processorchips on the same printed circuit board.
 7. The computer systemaccording to claim 1, wherein at least one processor chip on at leastone of the printed circuit boards of one of the groups comprises anetwork interface.
 8. The computer system according to claim 1, whereinthe one or more processor chips which are attached to one of the printedcircuit boards of one of the groups are connected to each of theprocessor chips of all printed circuit boards of the other group via atleast one network router and a network interface controller.
 9. Thecomputer system according to claim 1, wherein at least one processorchip on a printed circuit board of one of the groups is connected to aPCI Express card providing access to the PCI Express card for at leastone processor chip on another printed circuit board of the same group oranother group.
 10. A computer readable storage medium having computerreadable instructions stored thereon that, when executed by a computer,implement a method for connecting and communicating across a pluralityof printed circuit boards of a computer system, each printed circuitboard comprising two or more processor chips attached to the printedcircuit board and a plurality of connectors, wherein a first subset ofthe two or more processor chips are connected to a first subset of theplurality of connectors and wherein a second subset of the two or moreprocessor chips are connected to a second subset of the plurality ofconnectors, wherein the number of printed circuit boards is an evennumber greater than or equal to 4, the method comprising: arranging theprinted circuit boards in two groups, each group being arranged in adifferent stacking direction; and connecting the two or more processorchips, which are attached to each one of the printed circuit boards ofone of the groups, for communication to the processor chips of at leastone printed circuit board of the other group.
 11. The storage mediumaccording to claim 10, wherein the communication across the processorchips is performed via at least one of: a coherent shared memory access;a non-coherent shared memory access; providing access to a graphics,storage, communication or other adapter card attached via aPCI-interface; message passing using a network protocol; usingcommunication between two or more processor chips on the same printedcircuit board; and at least one network router and a network interfacecontroller connected to at least one processor chip on at least oneprinted circuit board.
 12. The storage medium according to claim 10,wherein a printed circuit board is unconnected by previously idling itsone or more processor chip via a hypervisor running on the computersystem.
 13. The storage medium according to claim 10, wherein thecommunication is tracked by a precise directory.